The GTAW process, sometimes also referred to as a tungsten inert gas (TIG) welding process, is a well known arc welding process used for joining a wide range of metals and alloys. The keyhole GTAW process is a high productivity variant of GTAW that is capable of the single pass, full penetration welding of metals and alloys that may, in some cases, exceed 12.7 mm in thickness. The keyhole GTAW process (K-GTAW) is described in Australian patent 744847, the content of which is incorporated herein by reference.
As will be seen from Australian patent 744847, the described K-GTAW process typically requires the welding current to be between three hundred and eight hundred amps. It also requires the generated welding arc to have highly stable and reproducible characteristics; one such characteristic, contrary to other GTAW processes, being a high arc pressure. Having said that, most other conditions necessary for the described K-GTAW process are achieved in a manner consistent with the definition and general understanding of standard GTAW processes, and therefore without the addition of orifices and additional gas flows to constrict and modify the arc (as is the case in plasma arc welding).
Indeed, in the past, the described K-GTAW process has been implemented using a welding torch that was developed prior to the development of the K-GTAW process, namely the CSIRO-developed High Current TIG torch (HC TIG torch) described in U.S. Pat. No. 5,892,199. The HC TIG torch is the only commercially available torch known to be capable of reliably supporting the K-GTAW process, albeit in a manner designed primarily for research applications rather than industrial applications.
It is an aim of the present invention to provide a welding torch suitable for use with the K-GTAW process in an industrial environment.
Before turning to a summary of the present invention, it must be appreciated that the above description of the prior art has been provided merely as background to explain the context of the invention. It is not to be taken as an admission that any of the material referred to was published or known, or was a part of the common general knowledge in Australia or elsewhere.
It is also useful to provide an explanation of some of the terms that will be used to define the spatial relationship of the various parts of the welding torch of the present invention. In this respect, spatial references throughout this specification will generally be based upon the welding torch oriented to be used from above a generally horizontal work-piece. With this environment as the basis, various parts of the welding torch may then be defined with reference to such an orientation, allowing further references to “above” and “upper” or “below” and “lower”, or the like.
Also, some aspects of the present invention that may ultimately be claimed in isolation (and not in an in-use environment), may nonetheless be difficult to describe and understand in isolation. Thus, some of the following description does describe the invention and its embodiments in such an in-use environment (for example, a welding torch when used in a K-GTAW process). Of course, it must be appreciated that the use of such description to define the present invention is not to be seen as a limitation, and certainly is not to be seen as a limitation only to the in-use environment, unless that intention is clearly stated.